Flow cytometry has emerged as a valuable research and clinical diagnostic tool for evaluating phenotypic surface markers on leukocytes and platelets. During the last five years, a flow cytometry facility has been established in our laboratory which has been used in several basic and clinical immunologic collaborative studies. Examples of representative projects conducted this year are outlined below. 1. Anti-idiotypic antibodies. Two.projects under the direction of Suzanne Epstein, DBB, CBER have characterized anti-idiotypic expression in mice. One project evaluated the genetic patterns of idiotype expression in three mouse strains and the other project examined in vivo responses to an anti-idiotypic antibody. Our laboratory performed the flow cytometric analyses of the lymphocytes exhibiting immunoglobulin expression in these animals. 2. Characterization of.anti-human myeloid antibodies. In a collaboration with Keith Skubitz, Oncology Dept., Univerisity of Minnesota, we have characterized the leukocyte binding profiles to human neutrophils, monocytes and lymphocytes of more than 60 monoclonal antibodies generated by Dr. Skubitz to myeloid antigens. Additional studies are in progress to characterize the antigens binding these antibodies. Collaborative studies with our flow cytometry facility have resulted in four publications this year (see publications section: Leitman et al., 1989; Misplon et al., 1989; Skubitz et al., 1989; and Misplon et al., 1990).